The general goal of this research proposal is to study the mechanism of oxygen transport by using various synthetic hemoglobins with different colors, different oxygen-binding capacities, or with spin-label probes. Some of the synthetic proteins, including green myoglobin and heme-spin-labeled hemoglobin, that have the same oxygen-binding properties as those of native proteins can be used as markers for determining properties of native hemoglobins. Other synthetic hemoproteins having oxygen-binding properties differing from those of native hemoproteins can be used as reporter molecules for abnormal hemoglobins. It is also possible to prepare various hybrid hemoglobins in which only one type of subunit has a marker (green heme or spin-label). Accurate studies of oxygen binding to these hybrid hemoglobins will provide important information about the molecular mechanism of oxygen binding, particularly the mechanism of heme-heme interaction of hemoglobin. This synthetic hemoglobin will also be incorporated into the red cell membrane in order to study oxygen transport through the red cell membrane. In addition, the mechanism of oxygen supply to tissue will be studied by using organ perfusion and surface fluorometric techniques. These fundamental studies of hemoglobin will provide a basis for further understanding and treatment of hemoglobinopathies and disorders of oxygen transport.